Aldehyde dehydrogenase class 3 (ALDH 3) and transketolase (TKT) are expressed much more highly in the corneal epithelial cells than in any other tissue examined. Indeed, ALDH 3 appears to be present in the cornea at concentrations resembling that of crystallins in the lens. Histochemical tests showed that ALDH 3 is preferentially expressed in the corneal epithelial cell, with very little if any being found in the corneal stroma and endothelium or in the conjunctival epithelium. Sequence analysis of the 5' flanking region of the mouse ALDH 3 and TKT genes revealed numerous consensus sequences for the binding of transcription factors associated with oxidative stress responses, raising the possibility that induction by stress plays a significant role in the high expression of these genes in the cornea. A TATA box is present in the ALDH 3 promoter but not in the TKT promoter. Southern blot hybridization indicates that ALDH 3 and TKT are single-copy genes in the mouse. Transgenic mouse experiment using the bacterial chloramphenicol acetyl transferase gene have failed to identify regulatory elements in the first kbp of 5' flanking sequence or intron 1 of the ALDH 3 gene. The mouse TKT cDNA has been cloned and sequenced. It is 86 to 92 percent identical to the human and rat TKT cDNAs and encodes a protein 93 to 98 percent identical to the human and rat TKTs. Northern blots indicate that TKT mRNA is about 2.1 kb long and is 30 to 50 times more abundant in the cornea than in other tissues.